1. Field of the Invention
The present invention relates to oil injection lubrication for engines and more particularly to oil injection systems and methods for lubricating a two-cycle engine.
2. Description of the Related Art
In two-cycle engines, it is a common practice to mix lubricating oil with induction air to lubricate engine parts. Typically, the intake air is pre-compressed inside a crank chamber before being sent into the cylinders. In this type of two-cycle engine, oil is guided to an intake passage and further into the engine by the intake air. More specifically, the oil encounters the intake air inside the intake passage and is misted therein. The misted oil is then drawn into the crank chamber as the piston ascends and a valve opens to allow intake air to enter the crank chamber. The misted oil lubricates rotating parts in and around the crankshaft and within the interior wall of the cylinder.
In conventional two-cycle engines, fuel mixes with the intake air inside the intake passageway to reduce the viscosity of the oil which promotes misting of the oil. However, in direct injection-type two-cycle engines in which the fuel is directly sprayed into the combustion chamber, the viscosity of the oil drawn into the crank chamber is not reduced by dilution with the fuel. The undiluted liquid oil is, therefore, more difficult to convert into a mist. Since the oil may not be sufficiently misted in the intake air, the amount of oil supplied to the engine may be reduced. Insufficiently misted oil results in liquid oil depositing onto the interior surfaces inside the intake passageway. More liquid oil deposits on the surfaces within the intake passageway when the flow of intake air decreases, such as during low speed operation. Consequently, as engine speed increases, the increased speed of the intake air carries oil that has accumulated within the intake passageway in addition to oil newly discharged from the oil discharge pipes, which results in excess oil burning within the combustion chamber, evidenced by white smoke emanating from the engine.